This invention relates to a calculus disintegrating apparatus. A calculus disintegrating apparatus has been developed which producs spark discharges in a coeliac liquid surrounding a calculus to digintegrate the calculus by the resultant hydraulic impact wave. Such a calculus disintegrating apparatus generally comprises two electrodes set at the distal end of a probe inserted into a coeliac cavity and a power supply section which impresses D.C. impulse voltage on the electrodes to generate spark discharges across the electrodes. The power supply section provided with a capacitor causes the discharge current to flow across the electrodes for production of spark discharges. The electrodes are generally prepared from tungsten alloy, and are slowly consumed with time due to the impression of discharge energy. During the use of the electrodes, the end of the anode in particular is rounded, resulting in a rise in the voltage required for the initiation of spark discharges. When a spark discharge initiating voltage rises beyond the voltage with which the capacitor is charged, then spark discharges fail to be produced. This means that consumption of an electrode shortens the effective life thereof. Moreover, it is impossible to recognize the extent of the depletion of the electrode by the naked eye, thus failing to define an optimum point of time at which the used electrode is to be exchanged for a fresh one. While a patient is undergoing a treatment, it sometimes happens that the effective life of an electrode comes to an end. Such an event increases the time of treatment and the pain suffered by a patient.